Photosensitive materials, such as color photographic paper and the like, are generally provided with emulsion layers which comprise silver halide emulsions sensitive to rays of light in blue, green and red wavelength regions respectively, and therein are formed color images by incorporating into said emulsion layers so-called color couplers which can form their individual dyes by undergoing the coupling reaction with the oxidized developing agent which is produced upon development of the optically exposed silver halide emulsions. (In the incorporation of color couplers, each coupler is generally combined with the emulsion layer whose photosensitivity is in the wavelength region the color of which bears a complementary-color relationship to the dye formed from said color coupler.) As for the dye-forming couplers, pivaloylacetoanilides are examples of yellow dye-forming couplers, 5-pyrazolones and pyrazoloazoles are those of magenta dye-forming couplers, and phenols and naphthols are those of cyan dye-forming couplers.
Of these dye-forming couplers, phenols or naphthols which have so far been used as a cyan dye-forming coupler have drawbacks such that the dyes formed therefrom absorb light in the green region also because the main absorption curve they have in the red region, by which they can assume the hue of cyan, is broad on the shorter wavelength side, the dyes formed therefrom have a side absorption in the blue region in addition to the main absorption, and so on.
With the intention of removing drawbacks as described above, there have been proposed various couplers, for instance, the imidazole type couplers disclosed in JP-A-63-226653 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-03-61946, etc., the couplers having a structure formed by condensing a pyrazole ring and a nitrogen-containing 6-membered ring, which are disclosed in JP-A-02-135442, JP-A-02-136855, etc., and so on. However, they are not wholly satisfactory in view of the hue of developed colors, the color formability and the fastness of dye images.
For color prints in particular, though it goes without saying that the hue just after processing is important, it is also important to retain said hue forever (e.g., upon long-range storage). Under these circumstances, it has been sought the art to obtain cyan dyes which not only have excellent hue but also ensure excellent dye image stability even when stored under inferior conditions, e.g., under high humidity, exposure to light, or the like.